The supposed deal — over how to handle young immigrants protected under the Deferred Action for Childhood Arrivals program, which protects immigrants in the country illegally who were brought to the US as minors — was hammered out with Senate Minority Leader Chuck Schumer and House Minority Leader Nancy Pelosi over dinner at the White House on Wednesday.

Included among those who sought to gather the facts on what the tentative agreement entailed were Republicans. Particularly, GOP leaders who will be instrumental in getting such a deal through Congress.

At its base level, Trump, Schumer and Pelosi "agreed to enshrine the protections of DACA into law quickly, and to work out a package of border security, excluding the wall, that's acceptable to both sides," as the Democratic leaders said in a statement following their Wednesday night dinner with the president.

A number of questions remained, such as what Trump's plan is for his proposed wall along the US-Mexico border, whether Democrats and Trump had agreed to either codify DACA or sign the DREAM Act, which includes a pathway to citizenship, and what exactly would be in a package of beefed-up border security.

Senate Majority Leader Mitch McConnell, who spoke with Trump over the phone Thursday, said in a statement that he looks "forward to receiving the Trump administration's legislative proposal as we continue our work on" DACA and related immigration and border security issues.

House Speaker Paul Ryan, who also spoke with Trump on Thursday, said at his weekly news conference that "it's right and proper that the president talks with the other party." Ryan added that House Republicans won't "bring a solution to the floor that does not have the support of President Trump."

A number of other prominent Republicans also expressed support for such an agreement.

Sen. John Thune of South Dakota, the third-ranking Republican in the Senate, told Bloomberg that he's open "in principle" to the deal described by Democratic leaders and Trump.

Ohio Gov. John Kasich, who ran against Trump for the Republican presidential nomination, said he was "encouraged" by the developments and said Congress "should get this done in hours, not weeks."

Sen. Jeff Flake of Arizona, a frequent critic of Trump, offered "kudos" to the president "for pursuing agreement that will protect #Dreamers from deportation."

Others joined in too. Sen. Lindsey Graham of South Carolina told Fox News that such a deal "makes plenty of sense," while Sen. John Cornyn of Texas, the second-ranking Republican in the Senate, tweeted that "real border security & enforcement a precondition" to any such deal.

In order to get the majority of the party on board, Trump is going to have to do a hard sell of the agreement. Immigration reform, even with past Republican support, has failed when presented to the conservative base. But Trump has built up a credibility on the immigration issue with conservative hardliners that few in Washington, DC have.

"He's the only one who can sell it; he has to be the one out front on fixing DACA and getting this behind the GOP," Scott Jennings, a special assistant to President George W. Bush, tweeted. He added, "Base perceives border to be porous; any 'security' measures implemented must convince them you can no longer 'walk right in' to USA.

"Trump has most credibility w/ base to sell whatever 'border security' measures come forth, so it is on him to ABC (always be closing) w/ GOP," he wrote in a third tweet.

Another piece many Republicans will be watching moving forward is which protections DACA recipients will receive. Whether it's a codification of DACA or passing of the DREAM Act could have a huge effect on how rank-and-file Republicans react to a finalized deal.

While the DREAM Act would include a path to citizenship, DACA simply allows those protected by the program to stay in the country and work legally.

"Here the details matter greatly," Barry Bennett, a former Trump campaign adviser, told Business Insider. "Some kind of work visa versus citizenship. The good sign is that negotiations are happening. GOP controls the floor calendar in both houses, so nothing is going to pass that at least a majority of the majority would support."

But with Trump's popularity among his GOP base as high as it is, some doubt that offering up a significant form of amnesty would cause him to lose touch, even as many prominent immigration hardliners voiced displeasure with the agreement.

"That's what makes this so kind of hard to assess," a former top Republican Senate staffer told Business Insider. "Because he walks on water with his base."

"It may be the case that only Trump can solve the DACA issue with Chuck Schumer, because he has so much credibility on this issue," the former staffer continued. Trump's voters know "he believes in the law and believes in strong border security, and are suspicious of other Republicans who claim they do."

It's going to likely be up to Congress to "make sure the bones of this are conservative," they added.

"You have this kind of bizarre situation where the guy everybody trusts on the issue appears to be selling out, and everyone they don't trust are trying to get as conservative a product as possible," the former staffer said, adding that Trump may not get his typical level of "validation" from his "ordinary line of validators" in the conservative press on this agreement.

Still, "it's just impossible to say right now," what will happen, they said. "We've never seen anything like it."